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hyperfocal focusing

Discussion in 'Adapted Lenses' started by Adubo, May 11, 2011.

  1. Adubo

    Adubo SithLord

    Nov 4, 2010
    Globetrotter
    Andrew
    good day!

    ive been using alot of MF lenses and as how i do it, i use the LCD of my :43: to focus accurately. with film cameras, i use the split screen to get most shots in focus. i use my lenses wide open most of the time (f1.4-f2.8)

    i've been trying to research on how to do the "shoot from the hip and everything's in focus" thing... a.k.a hyperfocal focusing but to little avail (well, there are some tutorials but only displays landscape shots (which uses rather really small apertures)

    been wanting to learn how to do this for easier "candid snapshots" on the street and urban places.

    thanks in advanced


    andrew:smile:
     
    • Like Like x 1
  2. ~tc~

    ~tc~ Mu-43 Hall of Famer

    Oct 22, 2010
    Houston, TX
    The hyperfocal distance is the shortest distance you can focus at and have infinity in focus.

    Any depth of field calculator will show you the hyperfocal distance.
    Online Depth of Field Calculator

    As an example, using the 20/1.7 on m43 at f/1.7 requires you to focus at 52 feet away to have infinity in focus ... meaning anything closer than 26 feet will be out of focus.

    Stop that lens down to f/4 though and everything from 11 feet to infinity is in focus.

    Switch lenses to the 7-14 at the wide end f/4 and everything from 1' to infinity is in focus.



    If your goal is extreme depth of field so you never have to worry about focus, you have two options:
    - smaller aperture (bigger f/stop number)
    - shorter focal length
    - smaller sensor
     
    • Like Like x 1
  3. Adubo

    Adubo SithLord

    Nov 4, 2010
    Globetrotter
    Andrew
    thanks for the answer! but i have a couple of questions though

    a) how do i set the "sharp zone" in my image is my 17mm 2.8 has a fly by wire MF system (thus, no hyperfocal distance scale"?

    or does it depend on my aperture and subject distance alone?

    b) how can i manually compute for the distance? i saw some photos of manual lensesand have some (im holding one right now) and it does have that 16 11 8 5.6 4 2.8 2 1.7 aperture ring and another one (the hyperfocal distance scale underneath it)
    kinda looks like this

    16 11 8 5.6 4 2.8 2 1.7
    16 11 8 4 and then a red mark 4 8 11 16
     
  4. The best you can do with the native m4/3 lenses is to use the calculator to determine the hyperfocal distance for the aperture/s you want to use, and then autofocus the lens at an object that you estimate to be that distance away from you. After that, set the lens to MF. To avoid accidentally turning the focus ring I've seen an idea suggested here before of using a thick rubber band around the lens and focus ring.
     
  5. You might want to look into a laser tape measure. I think they are pretty cheap these days and could easily work out the distance from your camera to the subject. Also be aware that the focus ring numbers are likely to be off due to the fact that most of the 3rd part lens adapters focus past infinty.

    I'm not certain on this, but I think if you focus to infinty and then mark the spot where the lens focuses, you can then use that as your focus point (instead of the usual red diamond) and use your focus ring to that point.

    I had noticed this with my M42 adapter, it was a little off, but I have a Konica 40mm on a Konica adapter and when the lens is focused for infinity, the infinity mark is way over at f22 on the depth of field gauge, not in the center.

    Follow up: I picked up a laser tape measure and it is about useless for photographic purposes. If only measures off of hard vertical surfaces - like walls. People, trees, bushes and the like don't work. Also, it can't read a spot on the ground and hardly works out doors at all. Well, it will be handy in the tool box, but it's not going in the camera bag.
     
  6. Adubo

    Adubo SithLord

    Nov 4, 2010
    Globetrotter
    Andrew
  7. Pelao

    Pelao Mu-43 Top Veteran

    959
    Feb 3, 2010
    Ontario, Canada
    This can work quite well.

    As an example, with my GF1 / 20, I sometimes use the following:

    -set f/8
-set MF
    
-turn camera off then on
    -This puts everything from about 6 feet to infinity in focus
     
  8. Adubo

    Adubo SithLord

    Nov 4, 2010
    Globetrotter
    Andrew
    Hi Pelao,

    I should check this on my Oly mft if this can be done. Thanks for the technique!

    Sent from my iOS using Mu-43 App
     
  9. Streetshooter

    Streetshooter Administrator Emeritus

    Dec 15, 2009
    Phila, Pa USA
    The thing to remember about hyper focal distance is...
    Infinity is a constant. No matter what fstop you use, the far end of focus will be infinity.
    You control the foreground focus range by changing fstops.

    Look at a MF lens to see how this works. As you change f-stops and adjust the infinity mark to that given fstop, the close distance changes but infinity is always the far distance.
     
  10. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    Hyperfocal and the K number

    Contax G cameras were pleagued with the absence of DOF scale too.
    So, about 13 years ago someone devised and published the K number concept. Why K? 1) it's a constant; 2) check my nick, c'est chic.

    1. For a given film/sensor format every focal length gets a constant "K" number.
    2. For any "Av" f-stop : Hyperfocal distance (meters) = K/Av
    3. This K number is equal, in :43: format, to (f^2)/15.

    So, for a :43: 20mm lens, K=27.
    Suppose you shoot at f/4, the hyperfocal is 27/4=6.75 m
    Note: I use 28 instead of the calculated 27. It just divides easier! Remember the hyperfocal concept is a series of approximations, so 7 or 6.75 m don't change much in the actual print.

    Just for you :smile: here's a table of :43: common focal lengths, with their respective K number. Forget telephotos: who would focus long lenses with hyperfocal distance?

    Focal length :)43:) / K number (metric):

    • 7 mm --> 3.2
    • 10mm --> 6.6
    • 14mm --> 13
    • 17mm --> 20
    • 20mm --> 28 :wink:
    • 25mm --> 42
    • 45mm --> 135

    Remember: the hyperfocal distance is K/Av. It's a good idea to write each lens K number(-s, for zooms) on a patch of paper taped to the outside of the lens hood.

    The DOF always extends from the hyperfocal distance (H) to infinity behind, and to H/2 in front.
    If you have a 20 mm set at f/4, this means the hyperfocal distance is 7m, so your shot will be sharp enough from 3.5 m to infinity.
     
    • Like Like x 8
  11. Streetshooter

    Streetshooter Administrator Emeritus

    Dec 15, 2009
    Phila, Pa USA
    Pan... That is toooo cool.
    I eat stuff like that up. Thanks ever so much.
    Don
     
  12. Adubo

    Adubo SithLord

    Nov 4, 2010
    Globetrotter
    Andrew
    Thats a neat trick! Thankyou Pan!

    Sent from my iOS using Mu-43 App
     
  13. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    µ4/3 K numbers in FEET

    Since some people managed to have a revolution, yet stick to Royal (or Imperial) units, here's the K numbers in 1/5.280 of miles :biggrin:

    It also happens that they're easier to remember than the metric version:
    God save the foot!

    Focal length :)43:) / K number (feet):

    • 7 mm --> 11
    • 10mm --> 22
    • 14mm --> 43 (Use 45!)
    • 17mm --> 64
    • 20mm --> 87 (90 does it!)
    • 25mm --> 137 (128, same thing!)
    • 45mm --> 443 (450 good enough)

    Note that for the sequence of easy memorization, you can round the sequence of K's for common "f/stop" numbers : 11 - 22 - 45 - 64 - 90 - 128 ... I think I'll forget the 45 mm lens K--I never used such a crazy f/stop!

    And there's no way I'll do it in US Survey furlongs, or Nijniy-Novgorod versta. Forget it.
     
  14. aria

    aria Mu-43 Regular

    50
    Oct 9, 2010
    Rome, Italy
  15. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    DOF scales on legacy lenses

    Just in case... This may be of some importance to those who practice "zone" focusing.

    35mm legacy lenses users should be warned that their DOF scale is wrong for :43: format. You should double the indicated f/stop value to keep consistent.
    I.e. where the DOF scale will read "4", use f/8...
     
  16. Streetshooter

    Streetshooter Administrator Emeritus

    Dec 15, 2009
    Phila, Pa USA
    Pan, thanks for this again. In my old age, I forgot to mention the crop factor in my above post.
     
  17. I made a quick table in Excel using the formulas Pan provided and then compared them to the tables available at http://www.dofmaster.com/doftable.html . While there are minor differences between the rule of thumb formulas and the dofmaster tables, there does not seem to be any doubling of the f value. Perhaps this is because I am using true focal lengths, not the crop factor apparent focal length?

    The Excel table is pretty brief, has the focal lengths of all my 3rd partly lenses, and can be printed on a half page of paper and put in my bag. You can take a copy from http://cid-6cf998413a2b7d24.skydrive.live.com/redir.aspx?page=view&resid=6CF998413A2B7D24!212 . The table is set up so that you can change the focal lengths of the preferred lenses to match your kit and the table will update accordingly.

    Now to see if I can find a laser/sonic measuring device that will reflect from a spot on the ground. I don't know if they work this way. I think they have to bouce off a wall or something perpendicular.
     
  18. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    Sorry, but I'll stick to my geometry and optics basics, so it's firmly "no".
    When you calculate DOF, there are three factors involved, and you seem to miss one:

    1. The focal length (of course the optical one, not "corrected")
    2. The f/stop
    3. The circle of confusion, which is directly derived from the physical sensor format.

    The generally accepted Circle of Confusion value is 1/1500 of the standard focal length of the given format (1/1000 for large formats starting from 2"1/4). This is what the DOF scale of any manufacturer's lens is based on.

    In 24x36 it's 45mm/1500=0.03mm
    In :43: it's 22mm/1500=0.015mm

    This means that if you take a 25mm lens, it will have twice the DOF in 24x36mm than it has in :43:

    For a demo, take a look at Cosina-Voigtländer's :43: 25mm Nokton, compare its scale with the same manufacturer's 25mm f/4 Color Skopar made for Leicas.

    When both lenses are set to infinity:
    On the Color Skopar, the f/8 mark is just a bit to the right of 7 ft.
    On the Nokton, it's the f/16 line which points just a bit right of 7 ft.

    Q.E.D.
     
  19. Pan, this is the piece I'm missing:

    This means that if you take a 25mm lens, it will have twice the DOF in 24x36mm than it has in u43

    Since the crop factor is just taking a portion of the image out of the center of a larger image normally produced by the lens, how would the depth of field change?

    Use an exampe of a photo with two objects close and far but in close alignment so that they would appear in the imager of both a full frame image a u43 image. Would they not look exactly the same, including the DOF?
     
  20. Pan Korop

    Pan Korop Mu-43 Veteran

    479
    Mar 31, 2011
    Phare Ouest
    The whole DOF concept is based on one's vision of a "standard" print, i.e. 8x10" US or A4 europ. held at a comfortable reading distance.
    So if you take only the "core" of the lens image with a half-width neg/sensor, you have to enlarge it twice more. Hence, every marginally sharp detail appears twice as big, and so goes the blur.

    PS: If it helps, let's put it the other way around: you got a 25 adapted from a 35mm cam. Shoot with the big DSLR, using the DOF scale. Blow up, i.e. print to 24x36cm size. Set the same lens, same f/stop, same tripod place, on the:43: camera. Use the same DOF scale. Print a 13x17cm print. Same image, but cropped. Now you get the same DOF on print: you just didn't enlarge to the same size.